I’ve just made a similar post, before coming across this post.
Its seems things haven’t progresssed very far since May (Autocomplete, IndexTable with bulk actions etc.). I too looked for good examples of where Shopify has used web components in their admin UI and apps, and have found none.
It’s made app development much more time consuming. I’m currently battling with grids to create a simple bulk actions and filter bar in the s-table component, something that would have taken 5 minutes before with the IndexTable component.
Sigh.